Second seed Stanislas Wawrinka needed almost three hours to beat Victor Hanescu of Romania 6-7 (2), 6-1, 7-6 (4).
In a late match, No. 5 seed Juan Monaco defeated fellow Argentine Eduardo Schwank 7-6 (5), 6-2.
Earlier, eighth-seeded Juan Ignacio Chela of Argentina defeated countryman Horacio Zeballos 7-5, 6-2.
AP, DUBAI, UNITED ARAB EMIRATES
Anna Chakvetadze collapsed on court on Wednesday and had to retire from her match with top-seeded Caroline Wozniacki.
The 23-year-old Russian was serving for the second set at 5-3.
After a long rally that Wozniacki won, Chakvetadze wobbled before fainting. She was given extensive medical treatment during a seven minute delay and returned for one more point before forfeiting the match and tearfully hugging Wozniacki.
Organizers said Chakvetadze, who lost the first set 6-1, had a stomach illness.
Wozniacki said it was a “shock” to see someone she considers a good friend collapse so suddenly. When she approached her, Chakvetadze said she had felt dizzy.
“Suddenly, I just see her collapse on the court. I didn’t know what happened,” the 20-year-old Dane said. “It was a shock. It was scary. To see someone collapse on other side, it’s not a nice sight. I just want to make sure she was OK.”
Wozniacki, who needs to reach the semi-finals in Dubai to retake the No. 1 spot she lost on Monday to Kim Clijsters, looked like she was coasting to an easy victory after winning the first set in 22 minutes. However, Chakvetadze woke up in the second and seemed on the verge of leveling the match.
“In the first set, I didn’t get into the game that much,” Wozniacki said. “She was making a lot of mistakes. Suddenly, she started to go for it. I just need some time. I started playing better at the end of the second set.”
In the first big upset of the tournament so far, Australian Open finalist Li Na wasted four match points in a 6-7 (6), 7-6 (6), 6-2 loss to Belgian Yanina Wickmayer.
The fifth-seeded Li led 6-2 in the second set tiebreaker before Wickmayer reeled off the next six points to level the match.
The 25th-ranked Belgian broke for a 4-2 lead in the deciding set when Li double faulted. Li then hit a forehand long to make it 5-2 on the way to the Belgian’s victory.
In afternoon matches, Francesca Schiavone and Svetlana Kuznetsova both won to set up their first clash since their nearly five-hour-long epic at the Australian Open.
Schiavone accounted for Chinese qualifier Zhang Shuai 6-3, 6-1 while Kuznetsova took the long road to beat Tsevetana Pironkova of Bulgaria 5-7, 6-2, 6-4.
Fourth-seeded Sam Stosur thrashed Sara Errani of Italy 6-0, 6-1 in 55 minutes, and seventh-seeded Victoria Azarenka of Belarus beat Chinese qualifier Peng Shuai 4-6, 6-2, 7-6 (5).